Textile yarn made from most synthetic filaments have been coated with a sizing material during their forming to improve the handibility of the filaments. However, yarns formed from these filaments were generally not acceptable in the textile industry. This was because most sizings applied at forming did not contain the characteristics necessary for processing the filaments into a high quality textile yarn.
To overcome this problem it has been a general practice to apply a sizing at forming that could later be removed. The main purpose of this sizing was to give the filaments handibility for later processing. Once the filaments had been processed the forming sizing would be removed and replaced with a finish sizing. The finish sizing usually would possess characteristics that would allow the filaments to be made into a high quality textile yarn.
The major disadvantage to this process was that the additional processing of the filaments necessitated by the two applications of sizing increased the cost of the end product textile yarn. Thus, a process for coating synthetic filaments that eliminate this two step process would improve the economics of making textile products from synthetic filaments.